Heretofore, a recording medium shaped like a disc such as an optical disc, magnetic disc, magneto-optical disc or the like has a spiral groove formed thereon for the purpose of tracking. It is already known to record address information by wobbling the groove adaptively to the address information.
Address information to be recorded to a disc-shaped recording medium is composed of a sync signal indicative of an address start position and an address indicative of address data itself. Some of address information further contain an error correction code (ECC) for the address data.
Since a sync signal included in address signal is not sufficiently long, it cannot have any ECC appended thereto. Unless a sync signal in address information can be reproduced accurately, address data having an ECC appended thereto cannot be reproduced either. In other words, the error rate of address information depends upon whether a sync signal in the address information can be reproduced accurately or not. Therefore, a method of accurately reproducing a sync signal in address signal should desirably be established.